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United States Patent |
5,089,330
|
Sato
,   et al.
|
February 18, 1992
|
Abrasive tape in which a single compound serves to improve dispersion of
abrasive particles and also as antistatic and lubricant for the tape
Abstract
An abrasive tape comprises a flexible substrate and an abrasive layer which
is overlaid on the flexible substrate and which contains abrasive grains,
a binder, and an additive. The additive contains at least one kind of a
compound represented by the general formula of
##STR1##
where R.sub.1 represents a monovalent hydrocarbon group having six to 30
carbon atoms, or a fluorine-substituted alkyl group having one to 17
carbon atoms, R.sub.2 represents H or a monovalent alkyl group having one
to three carbon atoms, X represents either one of
##STR2##
where R.sub.3 is C.sub.3 F.sub.7 and n is an integer of 1 to 30.
Inventors:
|
Sato; Masami (Kanagawa, JP);
Fujiyama; Masaaki (Kanagawa, JP);
Nishikawa; Yasuo (Kanagawa, JP);
Iwasaki; Takashi (Kanagawa, JP)
|
Assignee:
|
Fuji Photo Film Co., Ltd. (Tokyo, JP)
|
Appl. No.:
|
642156 |
Filed:
|
January 17, 1991 |
Foreign Application Priority Data
| Sep 30, 1988[JP] | 63-247220 |
Current U.S. Class: |
428/843.3; 428/329; 428/687; 428/900; 508/548; 508/562; 508/568; 508/570 |
Intern'l Class: |
G11B 005/71 |
Field of Search: |
428/900,329,694,323,687,695
51/295
252/52 A,45
|
References Cited
U.S. Patent Documents
4187345 | Feb., 1980 | Yamaguchi et al. | 428/337.
|
4701375 | Oct., 1987 | Nishimatsu et al. | 428/336.
|
4764423 | Aug., 1988 | Yamaguchi et al. | 428/323.
|
4770941 | Sep., 1988 | Imai et al. | 428/411.
|
Primary Examiner: Cashion, Jr.; Merrell C.
Assistant Examiner: Resan; Stevan A.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak & Seas
Parent Case Text
This is a Continuation of application Ser. No. 07/414,346 filed Sept. 29,
1989 now abandoned.
Claims
We claim:
1. An abrasive tape comprising a flexible substrate and an abrasive layer
which is overlaid on said flexible substrate and which consists
essentially of abrasive grains, a binder, and an additive, wherein said
additive contains at least one kind of a compound represented by the
general formula of
##STR10##
where R.sub.1 represents a monovalent hydrocarbon group having six to 30
carbon atoms, or a fluorine-substituted alkyl group having one to 17
carbon atoms, R.sub.2 represents H or a monovalent alkyl group having one
to three carbon atoms, X represents either one of
##STR11##
where R.sub.3 is C.sub.3 F.sub.7, and n is an integer of 1 to 30.
2. An abrasive tape as defined in claim 1 wherein the hydrocarbon group
which R.sub.1 in said general formula represents has six to 22 carbon
atoms.
3. An abrasive tape as defined in claim 2 wherein the hydrocarbon group
which R.sub.1 in said general formula represents has eight to 18 carbon
atoms.
4. An abrasive tape as defined in claim 1 wherein the fluorine-substituted
alkyl group which R.sub.1 in said general formula represents has six to 12
carbons atoms.
5. An abrasive tape as defined in claim 1 wherein R.sub.2 in said general
formula represents a monovalent alkyl group having one to three carbon
atoms.
6. An abrasive tape as defined in claim 1 wherein X in said general formula
represents
##STR12##
7. An abrasive tape as defined in claim 1 wherein n in said general formula
represents an integer of 1 to 22.
8. An abrasive tape as defined in claim 1 wherein said abrasive grains have
a Mohs hardness of not lower than 6.
9. An abrasive tape as defined in claim 8 wherein said abrasive grains have
a Mohs hardness of not lower than 8.
10. An abrasive tape as defined in claim 1 wherein at least one kind of
said compound represented by said general formula is added in proportions
within the range of 0.5 to 3 wt % with respect to the total amount of the
solid contents in said abrasive layer.
11. An abrasive tape as defined in claim 10 wherein at least one kind of
said compound represented by said general formula is added in proportions
within the range of 0.5 to 2 wt % with respect to the total amount of the
solid contents in said abrasive layer.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an abrasive tape which is used to polish a
magnetic head or the like. This invention particularly relates to an
abrasive tape which is used for finish polishing of a rough-polished
surface of a magnetic head or the like.
2. Description of the Prior Art
Video or high-grade audio magnetic heads are made by being polished with
abrasive tapes. The abrasive tape comprises a flexible substrate, and an
abrasive layer overlaid on the flexible substrate. In order to provide the
abrasive layer, an abrasive coating composition consisting of abrasive
grains, a binder, additives and the like is applied onto the flexible
substrate and dried.
The term "abrasive tape" as used herein broadly embraces abrasive members
which take on the form of a long strip or a disk. In general, when the
surface of a magnetic head or the like is to be polished with a long
strip-like abrasive tape, two reels are positioned with the magnetic head
or the like intervening therebetween, and the abrasive tape is moved in
contact with the surface to be polished between two reels. In cases where
a disk-shaped abrasive tape is used, the disk is rotated in order to
polish a surface.
The abrasive tape is flexible and can snugly fit to a curved surface.
Therefore, the abrasive tape is more suitable for the polishing of the
curved surface of the magnetic head or the like than grinding wheels.
Also, the abrasive tape can achieve scratch-free, accurate polishing of
the surface to be polished, and is therefore indispensable to finish
polishing of a rough-polished surface.
In cases where the abrasive tape is moved in an polishing apparatus in
order to polish a surface of a magnetic head, it is necessary that
movement stability of the abrasive tape be kept good. Also, the surface of
the abrasive tape should be prevented from being electrostatically
charged. Furthermore, abrasive grains should be dispersed uniformly in an
abrasive layer of the abrasive tape. Specifically, if movement stability
of the abrasive tape is low, the abrasive tape will stick and slip on the
surface of the magnetic head and generate a chirping sound during
movement. In such cases, the surface to be polished cannot be polished
uniformly. If the surface of the abrasive tape is electrostatically
charged due to friction with the surface to be polished, ambient dust will
stick to the surface of the abrasive tape and will undesirably scratch the
surface to be polished. If abrasive grains are dispersed nonuniformly in
the abrasive layer of the abrasive tape, the abrasive grains will
agglomerate locally and will undesirably scratch the surface to be
polished.
Various methods have been proposed in order to solve the problems described
above. For example, in Japanese Patent Publication No. 62(1987)-37447, a
method is proposed wherein additives such as a lubricant and an antistatic
agent are added to an abrasive layer of an abrasive tape, and the
proportions of the additives are changed in order to adjust the
coefficient of friction of the surface of the abrasive tape. In U.S. Pat.
No. 4,764,423, a method is proposed wherein a fatty acid, a fatty acid
ester, silicone oil, and a surface-active agent are added to an abrasive
layer of an abrasive tape in order to improve movement stability of the
abrasive tape. Also, in Japanese Unexamined Patent Publication No.
61(1986)-265279, a method is proposed wherein a dispersing agent and an
antistatic agent, such as carbon black or titanium black, are added to an
abrasive tape.
However, with the proposed methods, the lubricant, the antistatic agent,
and the dispersing agent are added independently in order to improve tape
movement stability, to prevent electrostatic charging, and to improve
dispersibility of abrasive grains. Therefore, when these additives are
added to the abrasive layer of the abrasive tape so that all of the three
requirements are satisfied, the proportions of the additives to the
abrasive layer increase. As a result, strength of the abrasive layer
deteriorates, and polishing performance of the abrasive tape becomes bad.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide an abrasive tape
having an abrasive layer which contains small proportions of an additive,
improves movement stability of the abrasive tape, and is free of
electrostatic charging, and wherein abrasive grains are dispersed
uniformly.
Another object of the present invention is to provide an abrasive tape
which has substantially good polishing performance.
The inventors carried out studies in order to accomplish the aforesaid
objects, and found that a specific compound serves as a movement stability
improving agent, an antistatic agent, and a dispersing agent. In cases
where the specific compound is added as an additive to an abrasive layer
of an abrasive tape, an abrasive tape having good characteristics can be
obtained while the amount of the additive added is kept small.
Specifically, the present invention provides an abrasive tape comprising a
flexible substrate and an abrasive layer which is overlaid on said
flexible substrate and which contains abrasive grains, a binder, and an
additive, wherein said additive contains at least one kind of a compound
represented by the general formula of
##STR3##
where R.sub.1 represents a monovalent hydrocarbon group having six to 30
carbon atoms, or a fluorine-substituted alkyl group having one to 17
carbon atoms, R.sub.2 represents H or a monovalent alkyl group having one
to three carbon atoms, X represents either one of
##STR4##
and n is an integer of 1 to 30.
With the abrasive tape in accordance with the present invention, an
improvement in tape movement stability, prevention of electrostatic
charging, and an improvement in dispersibility of abrasive grains can be
achieved only by the addition of at least one kind of the compound
represented by the aforesaid general formula to the abrasive layer.
Therefore, proportions of the additive to the abrasive layer can be kept
lower than those employed when several kinds of additives are added in
order to achieve different effects. Accordingly, the polishing performance
of the abrasive tape can be kept good.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view showing an example of the polishing apparatus
wherein an embodiment of the abrasive tape in accordance with the present
invention is employed,
FIG. 2 is an enlarged view showing the abrasive tape and the magnetic head,
FIG. 3 is a schematic perspective view showing another example of the
polishing apparatus wherein an embodiment of the abrasive tape in
accordance with the present invention is employed, and
FIG. 4 is a sectional view of the polishing apparatus shown in FIG. 3.
DETAILED DESCRIPTION OF THE INVENTION
From the viewpoint of hydrophilic-lipophilic balance (HLB), the hydrocarbon
group which R.sub.1 in the aforesaid general formula represents should
preferably have six to 22 carbon atoms, and should more preferably have
eight to 18 carbon atoms. In cases where R.sub.1 represents a
fluorine-substituted alkyl group, it should preferably have six to 12
carbon atoms. For the same reasons, R.sub.2 should preferably represent a
monovalent alkyl group having one to three carbon atoms. Also, X should
preferably represent
##STR5##
and n should preferably represent an integer of 1 to 22.
By way of example, the compound represented by the aforesaid general
formula may be selected from the following compounds:
##STR6##
The compounds enumerated above are obtained from an ordinary reaction of
higher aliphatic alcohols with polyalkylene glycols. For example, a
polyethlene glycol ether which is one kind of the aforesaid compound is
obtained from a process wherein an alkaline catalyst is added to an
alcohol or a phenol, and ethylene oxide is introduced into the resulting
mixture at a temperature within the range of 120.degree. C. to 180.degree.
C. at increased pressures or normal pressures. The compounds enumerated
above are commercially available as, for example, Emulex 110, and Emulex
NP8.5 (supplied by Nippon Emulsion K.K.); Leonil, Pelegal, Diazopon A,
Igepal, and Emulphor (supplied by I.G. Farhenindustrie A.G.); Brij
(supplied by Atlas Powder Co.); Dispersant (supplied by Oronite Chemical
Co.); Emulgen, Levenol, Emasol, and Scourol (supplied by Kao Corp.);
Nonion (supplied by Nippon Oil & Fats Co., Ltd.); Noigen (supplied by
Dai-ichi Kogyo Seiyaku Co., Ltd.); and Liponox (supplied by Lion Corp.).
As the abrasive grains dispersed in the abrasive layer of the abrasive tape
in accordance with the present invention, any of materials which are used
generally and which have the polishing effects or scratch polishing
effects may be employed. For example, for this purpose, it is possible to
employ .alpha.-alumina, .gamma.-alumina, fused alumina, silicon carbide,
chromium oxide, cerium oxide, corundum, artificial diamond, .alpha.-iron
oxide, garnet, emery (major constituents: corundum and magnetite), silica,
silicon nitride, boron nitride, molybdenum carbide, boron carbide,
tungsten carbide, titanium carbide, quartz, tripoli, diatomaceous earth,
and dolomite. The abrasive grains should preferably have a Mohs hardness
of not less than 6, more preferably a Mohs hardness of not less than 8.
One of the above-enumerated materials may be used alone, or two to four
materials may be used in combination. The mean grain size of the abrasive
grains varies depending on the purposes of polishing. For example, when
the abrasive grains are used for rough polishing, the mean grain size
should preferably fall within the range of approximately 16 .mu.m to
approximately 1 .mu.m. When they are used for finish polishing, the mean
grain size should preferably fall within the range of approximately 1
.mu.m to approximately 0.1 .mu.m.
The binder contained in the abrasive layer of the abrasive tape in
accordance with the present invention may be a thermoplastic resin, a
thermosetting resin, or a reactive resin, which are known in the field of
binders, or a mixture of two or more of these resins.
The thermoplastic resin which may be used as the binder in the abrasive
layer of the abrasive tape in accordance with the present invention
generally has a softening point of 150.degree. C. or lower, an average
molecular weight falling within the range of approximately 10,000 to
approximately 300,000, and a polymerization degree falling within the
range of approximately 50 to approximately 2,000. By way of example, as
the thermoplastic resin, it is possible to use a vinyl chloride-vinyl
acetate copolymer, a vinyl chloride-vinylidene chloride copolymer, a vinyl
chloride-acrylonitrile copolymer, an acrylic ester-acrylonitrile
copolymer, an acrylic ester-vinylidene chloride copolymer, an acrylic
ester-styrene copolymer, a methacrylic ester-acrylonitrile copolymer, a
methacrylic ester-vinylidene chloride copolymer, a methacrylic
ester-styrene copolymer, a urethane elastomer, a nylon-silicone resin, a
nitrocellulose-polyamide resin, polyvinyl fluoride resin, a vinylidene
chloride-acrylonitrile copolymer, a butadiene-acrylonitrile copolymer, a
polyamide resin, a polyvinyl butyral resin, a cellulose derivative (such
as cellulose acetate butyrate, cellulose diacetate, cellulose triacetate,
cellulose propionate, nitrocellulose, ethyl cellulose, methyl cellulose,
propyl cellulose, methyl ethyl cellulose, carboxymethylcellulose, or
acetyl cellulose), a styrene-butadiene copolymer, a polyester resin, a
chlorovinyl ether-acrylic ester copolymer, an amino resin, a synthetic
rubber type thermoplastic resin, or a mixture of two or more of these
compounds.
The thermosetting resin or the reactive resin which may be used as the
binder in the abrasive layer of the abrasive tape in accordance with the
present invention generally has a molecular weight of 200,000 or less when
the resin takes on the form of a coating composition. When the coating
composition is applied onto a substrate and dried, the resin exhibits an
infinite increase in the molecular weight through the condensation
reaction, the addition reaction, or the like. It is preferable that the
resin of this type does not soften or melt before the resin decomposes
thermally. Examples of such resins are a phenol resin, a phenoxy resin, an
epoxy resin, a polyurethane hardening resin, a urea resin, a melamine
resin, an alkyd resin, a silicone resin, an acrylic reactive resin, an
epoxy-polyamide resin, a nitrocellulose melamine resin, a mixture of a
high-molecular weight polyester resin with an isocyanate prepolymer, a
mixture of a methacrylate copolymer with a diisocyanate prepolymer, a
mixture of a polyester polyol with a polyisocyanate, a urea-formaldehyde
resin, a mixture of a low-molecular weight glycol, a high-molecular weight
diol and a triphenylmethane triisocyanate, a polyamine resin, a polyimine
resin, and a mixture of two or more of these compounds. The binders
enumerated above are used alone or as a mixture of two or more thereof.
In general, the thermoplastic resin, the thermosetting resin, and the
reactive resin described above respectively have their major functional
groups, and one to six kinds of other functional groups. Each of said
other functional groups should preferably be contained in proportions
within the range of 1.times.10.sup.-6 eq to 1.times.10.sup.-2 eq per gram
of the resin. Examples of said other functional groups are acid groups
(which may take on the form of Na salts or the like) such as a carboxylic
acid group, a sulfinic acid group, a sulfonic acid group, a phosphoric
acid group, a sulfuric acid group, a phosphonic acid group, a phosphinic
acid group, a boric acid group, a sulfuric ester group, a phosphoric ester
group, and alkyl ester groups with these acids; amino acid groups;
amphoteric groups such as an aminosulfonic acid group, a sulfuric ester
group with amino-alcohol, a phosphoric ester group with amino-alcohol, and
an alkyl betaine group; amino groups; imino groups; imido groups; amido
groups; an epoxy group; a hydroxyl group; an alkoxyl group; a thiol group;
halogen groups; a silyl group; and a siloxane group.
As the polyisocyanate component which may be used in the binder, it is
possible to use, for example, isocyanates such as tolylene diisocyanate,
4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene
diisocyanate, naphthylene-1,5-diisocyanate, o-toluidine diisocyanate,
isophorone diisocyanate, triphenylmethane triisocyanate. As the
polyisocyanate component, it is also possible to use products of reactions
between the above-enumerated isocyanates and polyalcohols, and
polyisocyanates produced from condensation of two to 15 molecules of
isocyanate monomers. The polyisocyanates enumerated above should
preferably have an average molecular weight falling within the range of
100 to 20,000. Such polyisocyanates are commercially available as Coronate
L, Coronate HL, Coronate 2030, Coronate 2031, Myrionate MR, and Myrionate
MTL (supplied by Nippon Polyurethane K.K.); Takenate D-102, Takenate
D-110N, Takenate D-200, Takenate D-202, Takenate 300S, and Takenate 500
(supplied by Takeda Chemical Industries, Ltd.); Sumidur T-80, Sumidur 44S,
Sumidur PF, Sumidur L, Sumidur N, Desmodur L, Desmodur IL, Desmodur N,
Desmodur HL, Desmodur T65, Desmodur 15, Desmodur R, Desmodur RF, Desmodur
SL, and Desmodur Z4273 (supplied by Sumitomo Bayer K.K.). These
polyisocyanates may be used alone or as a mixture of two or more thereof
different in curing reaction properties. In order to promote the curing
reaction, compounds having a hydroxyl group (such as butanediol,
hexanediol, polyurethane having a molecular weight within the range of
1,000 to 10,000, and water), compounds having an amino group (such as
monomethylamine, dimethylamine, and trimethylamine), and catalysts such as
metal oxides may be used together with the polyisocyanates. The compounds
having a hydroxyl group or an amino group should preferably
polyfunctional. The proportions of the polyisocyanate used should
preferably fall within the range of 5 to 40 wt % with respect to the total
amount of binder components.
The compound, which is represented by the aforesaid general formula and
which is used as the additive in the abrasive layer of the abrasive tape
in accordance with the present invention, should preferably be added in
proportions within the range of 0.5 to 3 wt % with respect to the total
amount of the solid contents in the abrasive layer. More preferably, the
proportions of the compound should be within the range of 0.5 to 2 wt %
with respect to the total amount of the solid contents in the abrasive
layer. If the proportions of the compound are higher than 3 wt %, the
polishing performance of the abrasive tape will deteriorate. If the
proportions of the compound are lower than 0.5 wt %, it will not be
possible to obtain substantial effects in improvement of movement
stability, prevention of electrostatic charging, and dispersion of
abrasive grains.
The present invention will hereinbelow be described in further detail with
reference to the accompanying drawings.
With reference to FIG. 1, a tape wind-up reel 7 is rotated in the direction
indicated by the arrow A, and an abrasive tape 1 is fed from a tape feed
roll 6 in the direction indicated by the arrow. The abrasive tape 1 is
threaded over pass rolls 8, 8 so that it is contacted at a predetermined
lap angle with a magnetic head 5 which is to be polished. In this manner,
the surface of the magnetic head 5 on which the abrasive tape 1 slides is
polished by the abrasive tape 1. As shown in FIG. 2, the abrasive tape 1
comprises a flexible non-magnetic substrate 2, which may be constituted of
polyethylene terephthalate (PET), polyethylene-2,6-naphthalate or the
like, and an abrasive layer 3 overlaid on the flexible non-magnetic
substrate 2. The abrasive layer 3 slides on the magnetic head 5 and
polishes it. Specifically, as shown in FIG. 2, the abrasive layer 3 has
hard abrasive grains 4, 4, . . . protruded therefrom, and the surface of
the magnetic head 5 on which the abrasive tape 1 slides is smoothly
polished by the hard abrasive grains 4, 4, . . . In order to form the
abrasive layer 3, an abrasive coating composition constituted of the
abrasive grains 4, 4, . . . , a binder, and an additive which contains at
least one kind of the compound represented by the general formula of
##STR7##
defined above is applied onto the flexible non-magnetic substrate 2.
Preferable thicknesses of the abrasive layer 3 and the flexible
non-magnetic substrate 2 vary depending on to what shape the magnetic head
5 is to be polished. In cases where the abrasive tape 1 is to be used for
finish polishing of a S-VHS system magnetic head, the thickness of the
abrasive layer 3 should preferably be approximately 5 .mu.m when the
thickness of the flexible non-magnetic substrate 2 is 30 .mu.m. Also, the
thickness of the abrasive layer 3 should preferably be approximately 10 [m
when the thickness of the flexible non-magnetic substrate 2 is 23 .mu.m.
If the thickness of the abrasive layer 3 is excessively large, the
abrasive tape 1 cannot snugly fit to the magnetic head 5. Therefore, the
thickness of the abrasive layer 3 should preferably be not larger than 50
.mu.m.
The abrasive tape 1 in accordance with the present invention is suitable
particularly for the polishing of a magnetic head having a high
performance. However, the abrasive tape 1 in accordance with the present
invention may also be used for polishing a hard disk 15 as shown in FIGS.
3 and 4. In cases where the hard disk 15 is to be polished, it is
sandwiched between rubber rollers 18, 18, and the abrasive layers of the
abrasive tapes 1, 1 are pushed by the rubber rollers 18, 18 against both
surfaces of the hard disk 15. The hard disk 15 is then rotated in the
direction indicated by the arrow B so that both surfaces of the hard disk
15 are polished simultaneously.
The abrasive tape in accordance with the present invention broadly
embraces, in its scope, the abrasive tapes which take on the form of a
long strip, and abrasive disks which is constituted of a thin disk-shaped
substrate and an abrasive layer overlaid on the substrate.
The present invention will further be illustrated by the following
non-limitative examples.
EXAMPLES
Abrasive tapes were made under different conditions as described below. The
term "parts" as used hereinbelow means parts by weight (parts by weight of
solid contents).
EXAMPLE 1
An abrasive coating composition as shown below was applied to a thickness
of 5 .mu.m onto a 23 .mu.m-thick polyethylene terephthalate (PET)
substrate, and dried to form an abrasive layer. The substrate on which the
abrasive layer had been overlaid was slit to a width of 1/2 inch in order
to make an abrasive tape.
______________________________________
Abrasive coating composition:
______________________________________
.alpha.-Fe.sub.2 O.sub.3 225 parts
(granular, mean grain diameter: 0.11 .mu.m,
Mohs hardness: 5.0)
Cr.sub.2 O.sub.3 75 parts
(granular, mean grain diameter: 0.30 .mu.m,
Mohs hardness: 8.5)
Vinyl chloride resin 8.3 parts
(Vinyl chloride having an average molecular
weight of 2.6 .times. 10.sup.4 : 87 wt %,
epoxy group content: 3.5 wt %,
sodium sulfonate group content: 0.5 wt %,
where wt % is a value with respect to the
weight of the vinyl chloride resin)
Sulfonic acid group-containing polyurethane
4.8 parts
resin
(molecular weight: 25,000,
molecular weight per --SO.sub.3 H: 25,000)
Polyisocyanate 9.6 parts
(75 wt % ethyl acetate solution of a reaction
product of 3 mols of 2,4-tolylene diisocyanate
compound with 1 mol of trimethylolpropane)
C.sub.16 H.sub.33 O(CH.sub.2 CH.sub.2 O).sub.10 H
2.9 parts
(Emulex 110 supplied by Nippoon Emulsion K.K.)
Methyl ethyl ketone 100 parts
Cyclohexanone 100 parts
______________________________________
EXAMPLE 2
An abrasive tape was made in the same manner as that in Example 1, except
that the amount of the constituent represented by the formula C.sub.16
H.sub.33 O(CH.sub.2 CH.sub.2 O).sub.10 H was changed to 1.5 parts.
EXAMPLE 3
An abrasive tape was made in the same manner as that in Example 1, except
that the amount of the constituent represented by the formula C.sub.16
H.sub.33 O(CH.sub.2 CH.sub.2 O).sub.10 H was changed to 9 parts.
EXAMPLE 4
An abrasive tape was made in the same manner as that in Example 1, except
that a constituent represented by the formula of
##STR8##
(Emulex NP8.5 supplied by Nippon Emulsion K.K.) was used in lieu of the
constituent represented by the formula C.sub.16 H.sub.33 O(CH.sub.2
CH.sub.2 O).sub.10 H.
EXAMPLE 5
An abrasive tape was made in the same manner as that in Example 1, except
that a constituent represented by the formula of
##STR9##
was used in lieu of the constituent represented by the formula C.sub.16
H.sub.33 O(CH.sub.2 CH.sub.2 O).sub.10 H.
EXAMPLE 6
An abrasive tape was made in the same manner as that in Example 1, except
that a constituent represented by the formula C.sub.16 H.sub.13 OCH.sub.2
CH.sub.2 OH was used in lieu of the constituent represented by the formula
C.sub.16 H.sub.33 O(CH.sub.2 CH.sub.2 O).sub.10 H.
EXAMPLE 7
An abrasive tape was made in the same manner as that in Example 1, except
that a constituent represented by the formula C.sub.6 H.sub.13 O(CH.sub.2
CH.sub.2 O).sub.30 H was used in lieu of the constituent represented by
the formula C.sub.16 H.sub.33 O(CH.sub.2 CH.sub.2 O).sub.10 H.
COMPARATIVE EXAMPLE 1
An abrasive tape was made in the same manner as that in Example 1, except
that, instead of the constituent represented by the formula C.sub.16
H.sub.33 O(CH.sub.2 CH.sub.2 O).sub.10 H being used, 2.9 parts of butyl
stearate serving as a movement stability improving agent, 2.9 parts of
cationic antistatic agent (Elecond X-1-D supplied by Senken Kagaku K.K.),
and 2.9 parts of lecithin serving as a dispersing agent were used.
COMPARATIVE EXAMPLE 2
An abrasive tape was made in the same manner as that in Comparative Example
1, except that the cationic antistatic agent was eliminated from the
abrasive coating composition.
COMPARATIVE EXAMPLE 3
An abrasive tape was made in the same manner as that in Example 1, except
that the constituent represented by the formula C.sub.16 H.sub.33
O(CH.sub.2 CH.sub.2 O).sub.10 H was eliminated from the abrasive coating
composition.
The abrasive tapes of Examples 1 through 7 and Comparative Examples 1, 2,
and 3 were used to polish ferrite video heads. During the polishing, in
order to evaluate tape movement stability, an investigation was made as to
whether the abrasive tapes generate a chirping sound. After the polishing
was finished, the number of scratches generated on the surfaces of the
video heads were counted in order to evaluate the effects in prevention of
electrostatic charging and in dispersibility of the abrasive grains. Also,
the time required for polishing of the video heads was investigated in
order to evaluate the polishing performance, and surface roughness (Ra) of
the abrasive tapes were investigated. Table below shows the results of
these investigations and the results of overall evaluation.
In order to investigate the chirping sound, each abrasive tape was moved in
contact with a video head in the polishing apparatus, and an investigation
was made as to whether abnormal sound was or was not generated during the
movement. In order to investigate the number of scratches generated on the
surface of video head, the surface of the video head which had been
polished for one minute with each abrasive tape was observed with a
microscope, and scratches having a width of at least 2 .mu.m were counted.
The time required to polish the video head was the time required to polish
the ferrite video head by 1 .mu.m. The surface roughness (Ra) of the
abrasive layer of each abrasive tape was measured at a cut-off value of
0.8 mm, a stylus radius of 2 .mu.m and a stylus speed of 3 mm/sec.
TABLE
______________________________________
Scratches Time
on video Surface required
head roughness to polish
Overall
Chirping surface (Ra) (sec.) evaluation
______________________________________
Ex. 1 None 0 0.045 21 .largecircle.
Ex. 2 None 0 0.050 20 .largecircle.
Ex. 3 None 0 0.043 25 .largecircle.
Ex. 4 None 0 0.047 23 .largecircle.
Ex. 5 None 0 0.044 22 .largecircle.
Ex. 6 None 0 0.046 21 .largecircle.
Ex. 7 None 0 0.044 23 .largecircle.
Comp. None 0 0.040 98 X
Ex. 1
Comp. None 11 0.044 53 X
Ex. 2
Comp. Gener- 50 0.088 20 X
Ex. 3 ated
______________________________________
As is clear from Table shown above, the abrasive tapes of Examples 1
through 7 in accordance with the present invention exhibited good movement
stability and good dispersibility of abrasive grains. Also, the abrasive
tapes in accordance with the present invention were free of electrostatic
charging so that no dust which would detrimentally scratched the surfaces
of video heads adhered to the abrasive tapes. Moreover, the abrasive tapes
in accordance with the present invention had polishing performance which
was nearly equal to the polishing performance of the abrasive tape of
Comparative Example 3 which tape contained no additive, and it was
confirmed that the abrasive tapes in accordance with the present invention
had very good polishing performance.
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